This application relates to a method of molding a platform for an airfoil, wherein lost core elements are utilized.
Airfoils are known and are utilized in a number of applications. In one common application, airfoils are utilized in turbine and compressor sections for gas turbine engines. The airfoils have a platform which may be mounted to a rotor structure. In particular, static vanes associated with the turbine or compressor sections include airfoils and platforms.
The airfoils can be exposed to high temperatures, and thus it is known to circulate cooling air within passages inside the airfoils and platforms. Thus, the combined airfoil and platform must have openings to receive the cooling air, and to communicate the cooling air into internal passages.
To form passages in airfoils and their platforms, so-called “lost core” molding techniques have been utilized. In a lost core molding technique, an element is made of a material which can be leached or otherwise dissolved, and which bears the shape of desired openings and spaces in the airfoil and platform.
In the prior art, there has been a main body core, which has been placed in a mold, and then utilized as a lost core component to form openings in a final platform. Molten metal is moved into the mold, and solidifies around the cores. Then the cores are dissolved or leached, leaving cavities within the final part.
Typically, a large opening is formed at a top of the platform to receive cooling air delivered toward the airfoil. From this large opening, side openings extend into cooling chambers within the platform.
Typically, a portion of one of the cores has extended upwardly beyond the top surface of the platform to form an opening in the top surface once the core has been leached away. This opening then provides an access point such that a machine, such as an electro-discharge machine (EDM) is able to move in, and machine the rest of the large opening away.
At that point, the side openings must be formed such as by cutting into an intermediate part.